# How to compress a PDF without losing quality Canonical HTML: [https://pdfpix.com/guides/compress-pdf-without-losing-quality/](https://pdfpix.com/guides/compress-pdf-without-losing-quality/) Two of the four methods never touch a pixel: rebuilding the file and subsetting its fonts. The other two re-encode images, and even the raster method keeps the text, because every candidate is read back and refused if it lost more than 2% of the non-space characters. With no hard cap, use the no-target page and let the lossless half do the work. ## The half that costs nothing Two of the four methods never touch a pixel. The structural method rebuilds the document into a fresh file and leaves behind orphaned objects and old revisions that edits piled up over time. The font method subsets each embedded TrueType down to the glyphs the pages actually draw, so a font that shipped with 3,000 glyphs stops carrying the 2,700 your document never uses. Both are lossless in the sense that matters: every page draws the same, every word stays selectable, and every image keeps the pixels it had. On the public run the structural method produced the smallest file in 173 cases and the font method in 79. These savings are free, and with a generous cap they are often all the file needs. ## The half that costs something The image method re-encodes placed images at 150 dpi with mozjpeg at quality 75. The raster method renders whole pages at 150 dpi and picks its own quality from a sample of the pages. Both are lossy, and both are where a demand for a small file gets paid for. On the public run the raster method shipped in 361 cases, at a median quality of 60. Its floor is quality 60, and that floor exists so the method stops before the page turns to mush. At 60 the loss shows on a photograph. 150 dpi is the other lever, and it is a deliberate one. It is above the 96 dpi a screen shows and below the 300 dpi a print shop wants. If you are compressing something that will be printed at full size and inspected closely, that is the number to think about, not the quality figure. ## Text quality is not part of the trade The one thing never traded away is the text. Even the raster method, which turns the visible page into an image, redraws the page's own text on top in invisible render mode, so selection, search, copy and paste and screen readers all keep working on the compressed file. That is enforced, not promised. Every candidate is read back and compared to the source, and one that lost more than 2% of the non-space characters is refused rather than offered. On the public run, every one of the 554 cases that carried text kept at least 99.99% of its characters. ## Resolution is the setting people mean When someone says a compressed PDF looks bad, the cause is usually resolution rather than JPEG quality. An image placed at 600 dpi and re-encoded at 150 dpi has lost three quarters of its pixels, and no quality number brings them back. 150 dpi is chosen to sit above a screen and below a print shop. A page read on a laptop or a phone has nothing to gain above it. A page going to a commercial printer at full size does, and for that job compression is the wrong tool. Send the original. ## How to keep quality in practice Three habits protect quality more than any setting inside the tool. 1. Ask for the largest file the receiving system will take. Every KB you leave on the table is quality you keep. A form that caps at 2 MB should get a 2 MB target, not a 500 KB one chosen out of caution. 2. Cut pages before you cut quality. Removing four pages of appendix photos saves more than any quality setting and costs nothing on the pages that remain. 3. If you have no hard cap at all, [the no-target page](https://pdfpix.com/compress-pdf/without-losing-quality/) runs the same engine with the lossless methods doing the work and no number forcing a lossy result. When you do have a cap, [the compress tool](https://pdfpix.com/compress-pdf/) takes it directly. [The general guide](https://pdfpix.com/guides/how-to-compress-a-pdf/) covers which of the four methods your file will lean on, and [the compress hub](https://pdfpix.com/guides/compress/) lists the rest of the cluster. ## Questions and answers ### Is any PDF compression truly lossless? Two of the four methods are. Rebuilding the document and subsetting embedded fonts change no pixels and no characters, and with a generous cap they often do the whole job. ### At what quality does a compressed image start to look wrong? The raster method's floor is quality 60, and at 60 the loss shows on a photograph. On the public run, when it shipped, its median quality was 60. The text is not part of the picture, so it stays sharp at any quality. ### Does compressing a PDF blur the text? No. Text is redrawn as real text on top of any rasterised page, and the result is checked against the source before it is offered. Any candidate that lost more than 2% of the non-space characters is thrown away. ### What target should I pick if I care about quality? The largest one the receiving system accepts. Compression only costs quality when the target forces the lossy methods to work hard, so a generous cap usually gets solved by the lossless half and costs nothing at all. ## Related pages - [Compress PDF without losing quality](https://pdfpix.com/compress-pdf/without-losing-quality/): Make the file smaller without making the text or images worse. The file stays in your browser. No upload, no account needed. - [Compress PDF](https://pdfpix.com/compress-pdf/): Make a PDF smaller without turning its text into a picture. The file stays in your browser. No upload, no account needed. - [How to reduce PDF file size](https://pdfpix.com/guides/how-to-compress-a-pdf/): Make a PDF smaller and know what got dropped. Free, in your browser, with Compress PDF. - [Make a PDF smaller](https://pdfpix.com/guides/compress/): Find the right guide for making a PDF smaller. Every guide on the job, sorted by the problem you have.